The uptake and metabolism of carbohydrates by lactic acid bacteria were studied. Sugar transport systems were analyzed by physiological, biochemical and molecular biological approaches. The structural gene for P-Beta-phosphogalactoside galactohydrolase (P-Beta-gal) determined by the 35 Kbp lactose plasmid isolated from Lactobacillus casei 64H (pLZ64) was cloned into pBR322 using Escherichia coli X1849 as the host organism. One recombinant plasmid (pLZ600) containing the 7.9Kbp Pst I B fragment of pLZ64 DNA, determined the enzyme. Minicell analysis of transformants containing various pLZ600 subclones was performed. Results revealed the position and direction of transcription of the P-Beta-gal gene and a gene that encoded an unidentified 43 kdalton product. The gene encoding P-Beta-gal, but not the other gene, was transcribed from an L. casei-derived promoter. A physical map of restriction enxyme sites in pLA64 was constructed. In other studies, it was demonstrated that 2-deoxy-D-glucose (2-DG) can inhibit growth of Streptococi without blocking metabolism via a futile cycle of 2-DG uptake, 2-DG 6-phosphate cleavage, and 2-DG expulsion that dissapates PEP.